This study examines the genetic and environmental risk factors leading to suicidal and self-harm behaviors in a representative community sample of female adolescents and young adults, and racial differences in the relative strength of these risk factors. The study objective is to clarify the impact of individual-level risk factors (including genes, environment, and personality traits) on suicidal and self-harm behavior. Suicidality and deliberate self-harm pose a considerable public health burden, yet there is limited research on risk factors for these behaviors. The hypothesis is that genetic, shared, and nonshared environment affect both self-harm and suicide attempts similarly. The hypothesis will be tested by means of a behavior genetic twin study design. Data, which have already been collected, come from a twin registry including over 3500 17- to 25-year old females (a demographic in which self-harm and suicidality are relatively common). It will first be determined whether the prevalence of these behaviors differs between African American and White young women. Structural equation modeling will also be used to 1) determine the extent to which genes, shared, and nonshared environment contribute to suicidal and self-harm behavior and whether those proportions vary by race, 2) determine whether common and/or unique risk factors contribute to suicidality and self-harm, and 3) test whether the personality traits of neuroticism and impulsivity account for some of the genetic influence on suicidality and self-harm. [unreadable] [unreadable] Several aspects of this study are unique: It will be the first behavior genetic analysis of self-harm and the first study of the differential prevalence of self-harm by race. Self-harm is increasingly common yet little understood. Also, this study will be the first to explore etiological similarities between self-harm and suicidal behavior. If similar risk factors contribute to both behaviors, prevention programs might easily be designed to target them simultaneously. The analysis of the differential impact of risk factors on self-harm and suicidality by race is also novel. If the relative impact of these risk factors varies by race, prevention efforts might most effectively target different classes of variables for different racial groups. Finally, no prior behavior genetic studies of suicidality have gone beyond estimating heritability to exploring the mechanism of genetic transmission. While genes are an unlikely target for prevention programs, it may be possible to target intermediate phenotypes such as personality styles. [unreadable] [unreadable] [unreadable]